As shown in FIG. 1, a conventional stethoscope includes a head 1, a rubber tube 2, ear tubes 3 and earpieces 4. When a user listens to multiple sounds with different audio frequencies, he or she usually needs to change the volume of a sound collecting chamber of the head 1. Namely, the user can change the volume of the sound collecting chamber when he or she needs to listen to both a high frequency sound and a low frequency sound.
As shown in FIG. 2 and FIG. 3, in the conventional stethoscope, a diaphragm 12 is disposed at a head body 14 and is fastened via a fastener 11. The fastener 11 is an annular rubber ring and wraps an annular step 121 of the diaphragm 12 and the head body 14 to fasten the diaphragm 12 to the head body 14.
When the conventional stethoscope is used, if the user would like to switch the listening frequency from a low frequency sound to a high frequency sound, he or she only needs to press the diaphragm 12 to make the diaphragm 12 contact the annular protrusion 145. At that moment, a λ angle of the diaphragm changes. However, since a lower surface 128 of the annular step is fastened to a platform 149 of the head body by the fastener 11, it is difficult to change the λ angle. The user needs to spend more effort to press the head body 14 to change the λ angle. As the result, the user may feel uncomfortable.
Furthermore, every user has his or her own audibility, preference and auscultation habit, but he or she cannot adjust the sound intensity of the conventional stethoscope, and can only use the predetermined frequency.
Furthermore, the conventional dual-frequency stethoscope head is not convenient to assemble, and it needs a skilled person to assemble carefully to ensure the hearing effect.
Moreover, if the hearing effect is reduced due to deviation during the operation process, the user cannot adjust the hearing effect by himself or herself.